(1) (n.) Geophysics. A representation of a physical property or entity that can be used to make predictions or compare observations with assumptions. Mathematical velocity models are commonly used to predict the depth to a formation of interest. Physical models, such as layers of clay or putty, can be used to simulate rock layers. As Sheriff (1991) points out, agreement between data and a model does not prove that the model is correct, since there can be numerous models that agree with a given data set. Alt. form: modeling. See: Convergence, Seismic Modeling. (2) (vb.) Reservoir Characterization. To produce a representation or a simulation of a problem. (3) (n.) Reservoir Characterization. A conceptual, three-dimensional construction of a reservoir or oil and gas field. The model is constructed from incomplete data and much of the interwell space must be estimated from nearby wells or from low vertical resolution data, such asseismic data. The construction of models can be performed by deterministic methods or geostatistical methods, or a combination of both. See: Vertical Resolution